About the 3.8L Jeep Wrangler EngineStarting in 1991, the 3.8L was a continuation of Chrysler's 3.3L V6. It was manufactured with a larger bore and new stroke to up the displacement. The engines themselves were built in Trenton, Michigan. The 3.3 also has a designation as an "EGA" engine and will sometimes be referred that way, while the 3.8L is an "EGH". The 3.3Ls are well known Chrysler work horse engines, and were even used in Shelby Can-Am race cars. After it was all said and done, and the last engine made, Chrysler had produced more than 5 million 3.3Ls.
3.8L Engine Vehicle FitmentWhile the 3.8L engine was used in several other Chrysler vehicles, such as their minivans, or even in a competitors Volkswagen Routan, it was only available in one Jeep model: The JK Wrangler. During the years 2007 to 2010/2011, it was the popular choice for an engine (no V8 was available), in both the 2-door Wranglers and the 4-door JK Unlimited versions.
3.8L Engine HorsepowerIt was only rated at 162 hp in the beginning, but by the time it reached it's production end in 2010, it's horsepower rating had grown to around 215 hp. Not too bad for a Jeep engine, considering that it would be in a short wheelbase, low weight JK Wrangler.
3.8L vs. 3.3L EngineWhile the cast iron 3.3L engine is similar to the later 3.8L, and is really a slightly older design, it was never available in a Jeep, only Chryslers. They do share some components, but most parts aren't interchangeable for a variety of reasons. The 3.3 was used many times in vehicles because it could be mounted transverse or in a longitude position in the engine bay. The 3.8L eventually got a lot of the good stuff taken from the 3.3, such as SFI, and forged connecting rods. Note that the Ford 3.8L, the Buick/GM 3.8L, or the Porsche 3.8L are entirely different engines and not related to the Chrysler/Jeep 3.8L V6 in any way.
Are you running the 3.8L Jeep engine in your Wrangler? How does it fare on the trails?